When the replacement for the Tappan Zee Bridge opened this week after four years of construction, its 3.1-mile arc over the Hudson River was buttressed by Pennsylvania steel.

High Steel, based in Lancaster, fabricated half the steel for the approach spans of the $4 billion Mario Cuomo Bridge's skeleton — nearly 800 girders, most measuring 12 feet deep and half up to a football field long. Hundreds of workers forged more than 50,000 tons of the custom-built "weathering steel" at the company's Williamsport plant.

"It's a once-in-a-lifetime bridge," said John O'Quinn, president of Pennsylvania's High Steel Structures. "Its opening is an historic event, a true success story for U.S. steel."

Its $120 million contract is the largest in High Steel's 86-year history. And in O'Quinn eyes, it marks an important milestone in rebuilding a quintessential Pennsylvania industry.

"It's a great time to be in American steel," O'Quinn said. "It could still be better. We're waiting for President Trump's infrastructure bill to get passed. "

As a candidate, Trump proposed spending $200 billion in federal funds as a catalyst for $800 billion in investments by states, cities, and the private sector, amounting to a $1 trillion outlay for the next decade.

Thousands of deficient and structurally obsolescent bridges are languishing across the nation. Many need to be replaced. The privately held High Steel, depending on the year, is either the country's largest or second-largest manufacturer of steel for bridges, along with Texas-based Hirschfield Industries.

The company is well-placed to fill the need. "We're fortunate. We're 500 miles from 50 percent of the U.S. population," said High's CEO Mike Shirk, who presides over four fabrication plants and an affiliated transportation company. "We're in the middle of a lot of economic activity and commerce."

The company, which employs 650 people, builds 200 bridges a year, Shirk said. To guarantee it could handle capacity for the Tappan Zee project, High invested $11.4 million to expand the Williamsport plant. About $430,000 of that was funded by a state economic development grant. Because of a shortage of skilled welders and machinists, the company also set up a job-training program.

"We had to ramp up our talent to handle the top-of-the-tier technology we were using," Shirk said.

Current projects include the replacement for the Scudder Falls Bridge on I-95 over the Delaware River, the Central Susquehanna Valley Project near Selinsgrove, and the Kosciuszko Bridge that links Brooklyn and Queens.

The original Tappan Zee carried an estimated 140,000 vehicles a day and was completed in 1955. According to a history of the bridge in the Atlantic magazine, the State of New York skimped on more expensive steel and then allowed roadway salt to corrode the bridge. The span was plagued by holes that sometimes gaped five feet wide.

The new bridge, named for former Gov. Mario M. Cuomo, is built to last 100 years.

The Oakland Bay Bridge was the nation's last major bridge project and, at about three miles long, roughly the same size as the Tappan Zee. Because of a loophole, since eliminated, Chinese steel was used in the California bridge's construction. O'Quinn said he expects a forthcoming case study will show that the Tappan Zee is a less expensive project. "We've become more efficient than ever before and provide more bang for the buck."

Transporting the gargantuan, blue-painted girders from Williamsport to Coeymans, N.Y., on the Hudson River required drivers able to delicately "thread the needle." Shirk rode along (video) on one of the deliveries and watched as the 130-ton beams slipped through narrow turnpike plazas between the toll booths.

"We literally had two inches of space on each side," Shirk said. "All those loads went through them. It was unbelievable. We didn't touch a one."